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Description

This is a pre-amp board for the HB100/GH100 microwave sensor.

The sensor unit is a 'homodyne' receiver, it mixes the received signal with transmitted signal to yield the difference beat tone between the two. The sensor unit has an IF output, the output frequency of the IF is proportional to speed of the object being measured:The formula listed is f = fo* [( C + Vr)/(C + Vs)] where C is wave velocity in medium, if free space @ 10.5 GHz would be close to 2.998E10 cm/sec, Vr is the velocity of receiver relative to medium, Vs is the transmitter velocity relative to medium. So its beat frequency output will be 2 times 10.5 GHz times the absolute velocity relative to a fixed object / speed of light. The amplitude will be a function of the strength of the reflected signal. Metal objects will be stronger then a hand.

Ordered five prototype PCBs last week from pcb-pool.com. They will be shipped next week. Wrote a small FFT sketch on my LPC1768-Mini-DK board to visualize the frequencies received by the HB100 sensor. They are in the rang of 0 to 2kHz for movements between 0 and 150km/h.